The functional portion mentioned is the portion with which the instrument is equipped in accordance with its task, i.e. for example a pointer tip in the case of a pointer instrument, a cutting edge in the case of a scalpel, or a fastening portion (the fastening portion is suitable for enabling the instrument to be attached elsewhere, in particular to other medical instruments, for example to a cutting block, an implant, a fraise, a saw, a drill, a chisel, a screwdriver, etc.) or a forcipate portion in the case of a pair of tweezers. It can also be or include a calibration receptacle which comprises a counter piece for an object to be aligned, for example in order to quickly register an image data set using a scanned counter piece. In everyday parlance, these functional portions are often also referred to as a “tip” of the instrument, and the term “tip” is also used here in this sense. It can thus also describe functional portions of instruments which are not physically embodied as a tip or embodied to be pointed.
Within the framework of navigation-assisted and/or image-guided surgery, the aforementioned pointers are in many cases used to register a patient, wherein a spatially tracked pointer is moved to various points and/or landmarks on the patient, in order to determine the spatial position of these points and/or landmarks in the navigation coordinate system of a treatment room. These points or landmarks are then assigned to corresponding points or landmarks provided in an image data set (CT, MRI, etc.) acquired for example before the treatment, and stored in the navigation system. On the basis of this, it is then possible to perform the navigation-assisted and/or image-guided treatment. In many cases, the instruments—i.e. including the pointer—are spatially tracked by optical tracking systems, wherein markings (tracking markers) attached to the instruments are tracked by cameras.
This sequence of registration steps is rather painstaking to complete using tracked pointer instruments in accordance with the prior art and conventional navigation systems, because the person performing the treatment has to constantly change their angle of view. In order to see which step follows as the next step in the registration procedure, it is necessary to look at the navigation monitor, while in parallel with this, the landmark on the patient is sought. In order to ensure that the landmark has been acquired, the surgeon again has to look at the monitor or wait for a confirmation signal. If a number of points or a point cloud (when acquiring surfaces) have to be scanned, the situation becomes even more difficult because the correct position of the pointer has to be verified again and again with the aid of the monitor—which is usually far away from the working environment.